In general, a diesel engine is a device that converts thermal energy into mechanical energy using a mixed gas of outside air and diesel fuel that is a kind of fuel as working fluid, and the mixed gas explosively burnt in a cylinder becomes exhaust gas to be discharged to an outside. In this case, a pipe that is connected to an exhaust port to discharge the exhaust gas to the outside corresponds to an exhaust pipe. The exhaust gas includes materials of carbon dioxide, monoxide, hydrocarbon, sulfur oxide, hydrogen sulfide, nitrogen oxide, ammonia, ozone, and oxidant, and if they are discharged in the atmosphere as they are, environmental pollution is generated. However, with the technical progress of diesel engines and apparatuses for reducing an exhaust gas, the discharge amount of harmful gases has been considerably reduced.
However, in order to solve environmental problems related to the global warming, ozone concentration in the atmosphere, and the like, the environmental standards for harmful gases that are discharged from vehicles have been gradually intensified, and particularly in the case of heavy equipment, the harmful gas discharge standards have been further intensified.
Accordingly, in the case of heavy equipment including an excavator in the related art, in order to satisfy Tier-4 Interim and Stage-IIIB that are diesel engine exhaust gas regulations, a diesel particulate filter (DPF) having diesel oxidation catalyst (DOC) provided therein is connected to a diesel engine exhaust port to oxidize monoxide (CO) and hydrocarbon (HF) and to collect particulate matters.
However, in the case of Tier-4 Final or Stage-IV to be intensified in future, regulations to reduce nitrogen oxide (NOx) are further intensified, and thus it is difficult to satisfy them using the current diesel particulate filter (DPF) only.
Further, unlike mufflers of general vehicles, the diesel particulate filter (DPF) in the related art is heavy, and if the DPF is directly mounted on an engine in spite that the filter provided therein is very vulnerable to vibrations, welded portions of the diesel particulate filter (DPF) are directly affected by vibrations due to engine driving and work loads to cause the occurrence of deformation, such as crack or damage.